Doubledutchchuck would be a good one to ask this question however I believe the change in energy by Lot # hit it's peak at Lot #12, I stand to be corrected on this but all my ASteel is in the lower Lot numbers.Lost

"It's not the game but the chase ~ not the trophy but the race !" from my Dad, many years ago.

As Lost stated, and which I agree with, the powders lots from #15 and later run very similar to one another. At least they do when comparing velocities across the chrono. Lot #17 may be slightly hotter than 15, but you won't notice any difference on the pattern board.Then last summer, I bought a one pound and 4 pound canister of Steel, neither having a lot number stamped on them. When I ran them across the chrono, the velocities they produced were exactly then same as the Lot 17 I have tested, and patterned identically. You can re-pattern your loads if you like, for self assurance, but I don't believe it is necessary, IMO.